Various heat transfer recording methods have been known so far. Among these methods, dye diffusion transfer recording systems attract attention as a process that can produce a color hard copy having an image quality closest to that of silver halide photography (see, for example, “Joho Kiroku (Hard Copy) to Soon Zairyo no Shintenkai (Information Recording (Hard Copy) and New Development of Recording Materials)” published by Toray Research Center Inc., 1993, pp. 241-285; and “Printer Zairyo no Kaihatsu (Development of Printer Materials)” published by CMC Publishing Co., Ltd., 1995, p. 180). Moreover, this system has advantages over silver halide photography: it is a dry system, it enables direct visualization from digital data, it makes reproduction simple, and the like.
In this dye diffusion transfer recording system, a heat-sensitive transfer sheet (hereinafter also referred to as an ink sheet) containing dyes is superposed on a heat-sensitive transfer image-receiving sheet (hereinafter also referred to as an image-receiving sheet), and then the ink sheet is heated by a thermal head whose exothermic action is controlled by electric signals, in order to transfer the dyes contained in the ink sheet to the image-receiving sheet, thereby recording an image information. Three colors: cyan, magenta, and yellow, are used for recording a color image by overlapping one color to other, thereby enabling transferring and recording a color image having continuous gradation for color densities. In the dye diffusion transfer recording system, the heat-sensitive transfer image-receiving sheet directly contacts with the ink sheet as described above. Therefore, surface properties (including releasing property, friction, unevenness (roughness) and the like) of the heat-sensitive transfer image-receiving sheet are important.
With the spread of the dye diffusion transfer recording system, a speeding up of the print speed is progressing in recent years. Consequently, such a problem has arisen that even though thermal energy is applied to a usual heat-sensitive transfer image-receiving sheet for printing, it is difficult to obtain a sufficient developed color density. Further, with respect to a thermal transfer image of the printed material, there is a demand for the image with higher density and more vividness. Accordingly, attempts have been made to improve transfer sensitivity. One of them is the improved method of increasing thermal energy at the time of printing so that a more vivid transfer density can be obtained. However, this method causes serious thermal damage to the heat-sensitive transfer image-receiving sheet. Consequently, the following problems are becoming more and more conspicuous. (1) An ink ribbon dye layer is heat sealed together with a dye-receiving layer of the heat-sensitive transfer image-receiving sheet as a transferee material, and (2) not only dyes of the ink ribbon dye layer, but also the dye layer itself is transferred to the heat-sensitive transfer image-receiving sheet as a transferee material (that is, so-called abnormal transfer occurs). When the heat-sensitive transfer image-receiving sheet used for a high speed printer is designed, it is necessary to consider the surface properties, especially the releasing property, different from those properties required for the heat-sensitive transfer image-receiving sheet at the time of a low printing speed as in the past.
Besides, the ink sheet is transported along with the image-receiving sheet. Therefore, a force generated by a friction between the surface of the image-receiving sheet and the ink sheet tends to affect to the transport of the ink sheet. Accordingly unless a friction force is within a suitable range, a lag occurs in the transporting of the ink sheet and the image-receiving sheet. Such a lag sometimes results in transporting troubles such as various kinds of unevenness owing to, for example, shear in transfer and ink sheet wrinkles, and also cutting of the ink sheet during transporting.
From the past, attempts have been made to devise and improve the surface properties (for example, releasing property, friction and roughness) of the image-receiving sheet (see, for example, Japanese patent Nos. 2572769 and 2854319, JP-A-2005-238748 (“JP-A” means unexamined published Japanese patent application), JP-A-59-214696, JP-A-62-105689, Japanese patent No. 2872781, and JP-A-2005-70251).
In Japanese patent Nos. 2572769 and 2854319, and JP-A-2005-238748, there are descriptions that wax, such as polyethylene wax, amide wax, Teflon (registered trade mark), and urethane-modified wax, is added as a releasing agent to a receptor layer of the heat-sensitive transfer image-receiving sheet. These publications disclose that releasing property can be improved by addition of this kind of the releasing agent. However, there is no description of friction between the ink sheet and the image-receiving sheet, namely influence to transporting properties. Besides, there is no description that fine particles for controlling roughness are added to the heat-sensitive transfer image-receiving sheet.
In JP-A-59-214696 and JP-A-62-105689, there are descriptions that organic-series fillers, such as styrene resins and urea-formalin polycondensation resins, are contained in the heat-sensitive transfer image-receiving sheet. However, a purpose of addition of these fillers herein described is to enhance a density of the thermal transfer image. At that time, the above-described problems caused by speeding up of the printer had not yet become conspicuous. Consequently, in JP-A-59-214696 and JP-A-62-105689, there is no description about the influence of the releasing property or friction between the transfer material and the transferee material upon the transporting properties, and releasing function given by the organic fillers.
Japanese patent No. 2872781 discloses that inorganic fillers are used as a modifier of the surface properties. However, the surface properties herein described is modified in terms of writing properties, and there is no specific description that the function to give releasing property can be attained by addition of particular inorganic fillers.
On the other hand, it has been studied from the past in the field of a silver salt photographic art to add fine particles thereby to provide unevenness on the surface from the viewpoint of glossiness control. Fine particles having functions to provide such the unevenness on the surface have been referred to as a matting agent. Studies on control of the surface unevenness have been made using said matting agent from the viewpoint of, for example, adhesion or friction control of the surface in addition to the viewpoint of glossiness control. As specific examples, a stick of films on each other, a scratch, deformation of the matting agent at the time of heat development, and a peeling off are becoming problems, so that various studies on the matting agent have been made (for example, JP-A-2005-70251).
However, in such a silver halide photographic light-sensitive material, no image is formed by transfer of dyes. Therefore, it is not necessary to consider releasing property between the transfer sheet and the image-receiving sheet. Further, it is not necessary to consider transfer inhibition and transfer unevenness of the dyes when the dyes are transferred from the transfer sheet to the image-receiving sheet.
JP-A-2006-48024 proposes to use a matting agent in the transfer material such as a color filter. However, the matting agent herein described is for use in a back layer rather than a transfer layer.